An emulsion is a dispersion of one liquid in another liquid and generally is in the form of a water-in-oil mixture having an aqueous or water phase dispersed within a substantially immiscible continuous oil phase. Water-in-oil (or oil in water) emulsions having a high ratio of dispersed phase to continuous phase are known in the art as High Internal Phase Emulsions, also referred to as “HIPE” or HIPEs. At relatively high dispersed aqueous phase to continuous oil phase ratios the continuous oil phase becomes essentially a thin film separating and coating the droplet-like structures of the internal, dispersed aqueous phase. In certain HIPEs continuous oil phase can have one or more polymerizable monomers. These monomers can be polymerized, forming a cellular structure, for example a foam, having a cell size distribution defined by the size distribution of the dispersed, aqueous phase droplets.
HIPE foams can be formed in a continuous process, wherein a HIPE is formed and then moved through the various stages used to produce a HIPE foam. A movable support member, such as a belt, will typically be used to move a HIPE from one stage to the next. Following the formation of the HIPE the next stage involves the polymerization of the monomers present in the oil phase to produce a HIPE foam. Initiator, which is used to start polymerization, is generally added during HIPE formation either to the separate aqueous and continuous oil phases or to the HIPE during the emulsion making process. In addition to the presence of initiator, heat can be used to accelerate the polymerization reaction, for example the individual aqueous and oil phases may be heated to accelerate the polymerization reaction.
After polymerization occurs, the resulting HIPE foam is saturated with aqueous phase that needs to be removed to obtain substantially dry HIPE foam. HIPE foams can be squeezed free of most of the aqueous phase by using compression, for example, by running the HIPE foam through one or more pairs of nip rollers. The nip rollers can be positioned such that they squeeze the aqueous phase out of the HIPE foam. Because there is a need to create HIPE foam with a level of uniformity, the saturated aqueous phase should be squeezed out while maintaining a uniform cross direction moisture and salt profile while increasing possible belt width.
Therefore there exists a need for a way to improve aqueous phase removal from a HIPE foam using a nip to create a uniform cross direction moisture and salt profile while increasing belt width.